1. Field of the Invention
The present invention concerns out-of-service conditions and more particularly, techniques for improving responses to out-of-service conditions.
2. Description of the Related Art
In recent years, the mobile communications industry has exploded in terms of subscriber growth. To meet the increased demand, wireless carriers have built various types of communications networks, which generally provide ample wireless coverage in populated areas. Even so, there are certain locations where coverage may be weak. For example, subscribers may experience poor coverage in enclosed spaces, such as an elevator or a basement. In addition, as a subscriber moves away from a populated area, there is a possibility that the subscriber will lose coverage.
When a mobile unit detects a loss of coverage, i.e., an out-of-service condition, the mobile unit will typically take steps to reacquire a wireless signal. For example, many handsets will scan for the system with which it last communicated and possibly other communication networks, both of which may be stored in a preferred roaming list (PRL). There is a balance that needs to be addressed when designing scanning techniques during an out-of-service condition. One competing interest is the need for the handset to scan frequently for the lost network and other available networks to enable quick re-acquisition of a wireless signal. The other concern is to ensure that the power drain on the handset from the out of service scanning is not too great as to cause a significant degradation in battery life. As a result, handset manufacturers are constantly seeking new techniques for scanning in out-of-service conditions.